I asked the question about a multiple tap transformer because I don't understand the details about how a part of a circuit gets "out of phase."

We're using the word phase in several different ways and that's part of the confusion at least for me.

I'm not sure it makes sense to say the two lines of a 240 volt service are 180 degrees out of phase even if technically they are, because that seems to imply a two phase supply, and that you can create an infinite number of phases with a multiple tap transformer.

In my blissful ignorance I just always considered one line to be +120 volts referenced to ground, and the other -120 volts. I'm pretty sure that's wrong, but at least it's not confusing.

I admit I don't understand the fine details here. So, suppose I take my 120 volt singlephase house current, and I connect two incandescent light bulbs in series, each with a resistance of 60 ohms. Total resistance is now 120 ohms so I should have 1 ampere of current flowing. If I measure the voltage across both bulbs I should have 120 volts; but if I measure from between the two light bulbs in either direction I will read 60 volts (and the bulbs won't be all that bright). (but I don't care, I'm not going to read by them; this is a thought experiment)

NOW: are those two voltages 180 degrees out of phase? If not, why not? This is exactly analogous to the center tapped transformer, with the sole exception that I didn't ground the center of the lightbulb circuit.

What if I used 4 bulbs? Etc.